Specialized telecommunications systems and services have been developed to serve particular telecommunication needs. An example of such a specialized telecommunications system is a Centrex telephone network, which may also be referred to herein as an extension service. Generally stated, a person using a telecommunications unit in a Centrex network may call another person in the same Centrex network simply by using a shortened dialing number such as a shortened form of a directory, unit, or extension number or other substitute rather than using the complete directory or unit number. For example, assume a business such as Tarheel Mfg. subscribes to a Centrex network that assigns a four digit extension to each of the telecommunications units used at Tarheel Mfg. An employee of Tarheel Mfg. may call a co-worker simply by dialing the co-worker's four digit extension. Advantageously, the employee does not have to retrieve and input any more than four digits in order to reach any other co-worker at Tarheel Mfg. In addition, the implementation of the Centrex network may save Tarheel Mfg. money over the cost of conventional telecommunications service provided to the telecommunications units used at Tarheel Mfg.
FIG. 1 is a block diagram of a Centrex telephone network 100 operated by a local exchange carrier (“LEC”). The network 100 includes a plurality of individual telephone lines 110-124. The telephone lines 110-124 are assigned to an organization or group of organizations. The LEC assigns each line a seven digit calling line number including a three-digit NXX prefix, and a four digit XXXX suffix, where “N” is a numeral between 1 and 9, and “X” is a numeral between 0 and 9. In addition, each line within the network is located within a geographic area, with several lines within a single area being assigned a Numbering Plan Area code (“NPA”). Thus, to call a line within the network from outside the network, the caller dials the NPA-NXX-XXXX of the particular line. Certain calls also may require an additional prefix of 0 or 1.
Although the lines 110-124 are part of a single organization, the lines need not be located in a single geographic location. For example, lines 110-116 may be located in Atlanta, Ga. Lines 118-124 may be located in Washington, D.C. Calls from lines 110-116 are switched through switching equipment, such as a computer, located in an end office 140. Calls from lines 118-124 are switched through switching equipment located in a second end office 142. The end offices 140, 142 may be coupled through one or more tandem offices 144.
Within the Centrex network 100, callers need not dial the entire NPA-NXX-XXXX to reach an internal calling line. Instead, internal callers dial only the four digit XXXX suffix (also referred to herein as “extension”). When the extension is dialed, callers are automatically switched to the calling line within the network containing that suffix. To prevent duplicate switching, all four digit XXXX extension within the network are unique.
This “automatic” connection between callers within the network is performed by one or more end office switches 140, 142. Each end office switch includes switching technology that connects calls from one group of calling lines to other lines connected to that switch. For calls to other calling lines, an end office may switch the call to another end office that is coupled to the destination calling line. Additional networking components may be involved, including Signaling System 7 (“SS7”) elements and Advanced Intelligent Network (“AIN”) elements. For additional information on the public switched telephone network (“PSTN”), SS7 and the AIN, the interested reader is referred to the commonly assigned patent to Weisser, Jr., U.S. Pat. No. 5,430,719, which is incorporated herein by reference.
The LEC assigns all of the lines 110-124 to a single “Class of Service” (“COS”). A COS includes a table or group of tables within a switch that specify how calls are to be switched from calls made from lines within the COS. For instance, lines 110-124 would be assigned to a single COS. All calls made from those lines would be assigned to a table or group of tables within the end office.
FIG. 2 illustrates a sample COS table 200 stored in an end office. The table 200 contains information for switching calls within Centrex network 100. The table 200 includes two fields. The dialed number field 220 contains a four digit XXXX suffix dialed by a caller within the Centrex network. The calling line number field 240 contains the full NPA-NXX-XXXX (or NXX-XXXX for areas where ten digit dialing is not required) corresponding to the directory number (DN) of the calling line. A directory number is also referred to herein as a calling line number. For example, referring to FIG. 2, a caller within the Centrex network dialing an extension of 4453 is connected to the party within the Centrex network, who has been assigned the extension of 4453, but whose calling line number is 404-555-4453. The table 200 may store additional information as well, such as the name of the party having the calling line number indicated in field 240.
Centrex networks or extension services have been welcomed by subscribers who enjoy the benefits of: (1) shortened dialing numbers for use in dialing others within the network or service; and (2) cost savings over conventional telecommunications services. These subscribers have sought ways to extend their Centrex networks to keep up with their changing telecommunications needs. A relatively recent change in telecommunications is the increased use of wireless units. A wireless unit may be a cellular phone, a personal communications system (PCS) device, pager, or the like.
For example, Tarheel Mfg. may employ a sales staff and equip each of its sales representatives with a wireless unit. Unfortunately, a typical Centrex network is a landline or wireline network, and as such, is unable to include a wireless unit as a terminating unit in the Centrex network. In other words, the president of Tarheel Mfg. is unable to reach the sales representatives through shortened four-digit dialing in the Centrex network. Rather, the president has to dial the complete unit number of the wireless unit of the particular sales representative the president is trying to reach. This can mean that the president has to retrieve and input up to ten digits to reach the particular sales representative. In addition, the president's call does not benefit from the cost savings that are accorded to calls in the Centrex network.
Therefore, there is a need for methods and systems that extend Centrex networks, extension services, and similar networks and services, to keep up with changing telecommunications needs of subscribers.
There is a particular need for methods and systems that extend Centrex networks, extension services, and similar networks and services so as to include wireless units as terminating units in a Centrex or similar network and/or to provide extension or similar services to the wireless units.